4 Questions About Capturing an Asteroid

Earlier this month, NASA said it would go ahead with the plan to snare a small asteroid and bring it into an orbit around the moon, where astronauts could study it and investigate the idea of mining the valuable resources inside these space rocks. PM contributor and NASA astronaut Tom Jones explains why the U.S. chose this mission rather than just returning to the moon.

The answer involves politics and money. Although the moon is just three days away and offers valuable resources such as water ice, the White House canceled NASA's Constellation program, and its plan to return to the moon, in 2010. At this point there is no chance the Obama administration will reverse course and adopt this Bush administration goal.

So, NASA had to find another nearby destination for future exploration, and the capture-an-asteroid mission gives the agency a near-term target just beyond the moon. NASA thinks it can get astronauts there on a month-long mission by the early 2020s. Given current budgets, the asteroid mission is the only realistic astronaut destination NASA can reach before 2025—a manned trip to Mars just isn't going to happen that soon.

The second attractive feature of the asteroid capture concept is that it could be the first step toward establishing a commercial enterprise in deep space, one that promises to lower the cost of space exploration by using energy and raw materials from the sun, asteroids, and the moon. Two private space-mining firms have already announced plans to prospect asteroids for water and valuable metals. The NASA mission will deliver a target for prospecting and mining tests just beyond the moon, inviting a public–private partnership to develop this industry.

Why Not Target the Moon's Resources Rather Than an Asteroid's?

The moon's great asset is its proximity, just 240,000 miles away. We know there is water ice at its poles, hidden in cold craters shadowed from the sun's heat. But getting at that ice, and using it, is a huge challenge.

Imagine driving a rover over rugged, cratered terrain in bone-chilling temperatures, then sifting tons of frosty regolith for water, and then launching it to lunar orbit. NASA doesn't have an approved robot prospector to locate and extract water from the moon, nor can it afford a way to launch that water (or the hydrogen and oxygen propellants produced from it) out of the lunar gravity well, which will require launch pads, reusable tanker rockets, and perhaps astronauts to oversee the operation. We should be studying this, but it's not going to happen soon.

The asteroid mission uses existing technology or tech that is within reach in the next decade. The needed solar electric propulsion and capture systems are both extensions of systems already flown on interplanetary probes and on space communications antennas. Because an asteroid has very low gravity, no lander is needed.

A spacecraft can pull right up to the water-rich clay minerals on the surface. A 500-ton captured asteroid might contain 50 to 100 tons of water. Concentrated sunshine can easily bake it free, and once the water is distilled, it can be stored right alongside the spacecraft. Water recovery and availability for use is much simpler for an asteroid operation than a lunar one.

Perhaps the biggest challenge will be to find a set of small asteroids within reach of the capture spacecraft. Small asteroids are dim and hard to see, so NASA will have to fund existing and off-the-shelf telescopes and link them for this new search. If NASA starts promptly, about two dozen possible candidates should be detected over the next five years.

A NASA–industry–international partnership to return and prospect an asteroid starts the U.S. on the road to opening a new commercial frontier in deep space. The goals should be to lower costs for future exploration and to grow profitable businesses off the planet.

Another asteroid retrieval benefit is that the mission would provide the first demonstration of how to deflect a rogue asteroid—to change its orbit and make it miss the Earth. NASA would be gaining valuable experience in protecting the home planet from a catastrophic asteroid impact down the road.

Is the Mission Affordable?

Yes. The proposed mission cost of $2.6 billion over 10 years is just over 1 percent of NASA's spending over the next decade. The asteroid retrieval is comparable in overall cost to the Mars Curiosity rover mission.

Once the asteroid is parked in lunar orbit, using it for research and resources will require repeated astronaut missions and visits by robot probes. NASA's current budget will not pay for that full suite of follow-up missions, but the initial results should convince policy makers to seize the opportunity to do great science, gain experience in human exploration, protect the planet, and kick-start deep-space industries. If we can afford to have explorers in deep space, then we should look at every opportunity to maximize the scientific and economic return from their work beyond the moon.

Does This Mean NASA Will Ignore the Moon?

NASA continues to do robotic science from lunar orbit. The recent GRAIL gravity mission was a smashing success, and the Lunar Reconnaissance Orbiter continues to return exquisite images from a very low lunar orbit. NASA has no plans to return astronauts to the moon under the current administration. China, meanwhile, plans for manned landings on the moon in the mid-2020s.

The technology for an asteroid capture mission—handling large masses in translunar space, teaming robots and astronauts to take on complex tasks in deep space, and extracting water (and thus rocket fuel) from alien material—could be applied just as easily to a future return to the moon. If in the 2020s the country can afford to develop a reusable lander, solar electric propulsion can deliver it to lunar orbit to carry Orion crews to the surface. Once back from the moon, the lander could be serviced and refueled cheaply using asteroidal or lunar-derived propellants. The asteroid retrieval mission gives us flexible technology and experience that can boost us back to the moon, as well as to more distant asteroids and Mars.

Tom Jones is a veteran astronaut and senior research scientist at the Florida Institute for Human and Machine Cognition. His website is AstronautTomJones.com.

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